Optical apparatus for regulating the combination and separation of reflected luminous beams

ABSTRACT

An optical system for combining or dividing two light beams for constant illumination of an image for observation and for instantaneous illumination for its photographic recording, excludes a reflecting member at the intersection of the beams. The system is of particular value in an ocular biomicroscope to combine beams from a flashing light source with that from a constant light source to provide a flat beam projected into the eye forming an image of a slit. The system also separates the beam from the image into two beams of appropriate intensities for viewing and recording respectively. The reflecting member for combining beams is a rectangular prism with a narrow, rectangular, inner totally reflecting inclined surface engaging only a part of the nonreflected beam. The reflecting surface for separating two beams is of elliptical shape. A partially reflecting surface in the prism can be moved into position replacing the totally reflecting surface and engaging the whole beam. The composite beam is a central flat beam from the flashing source and a beam separated into two lateral beams from the constant source, fused accurately in the slit image by the objective. A collecting lens is interposed between the reflecting surface and the slit.

United States Patent [72] Inventor Paul Frederic Marie Gambs 140, rueMaznod, Lyon, 2e (Rhone), France 2 1] Appl. No. 795,200

[22] Filed Jan. 30, 1969 [45] Patented July 6, I971 [32] Priority Mar.13, 1968 [33] France [54] OPTICAL APPARATUS FOR REGULATING 'll'llllECOMBINATION AND SEPARATION OF Primary Examiner-David Schonberg AssistantExaminer-Paul A. Sacher Attorney waters, Roditi, Schwartz and Nissen tit CT: An optical system for combining 0r dividing two light beams forconstant illumination of an image for observation and for instantaneousillumination for its photographic recording, excludes a reflectingmember at the intersection of the beams. The system is of particularvalue in an ocular biomicroscope to combine beams from a flashing lightsource with that from a constant light source to provide a flat beamprojected into the eye forming an image of a slit. The system alsoseparates the beam from the image into two beams of appropriateintensities for viewing and recording respectively. The reflectingmember for combining beams is a rectangular prism with a narrow,rectangular, inner totally reflecting inclined surface engaging only apart of the nonreflected beam. The reflecting surface for separating twobeams is of elliptical shape. A partially reflecting surface in theprism can be moved into position replacing the totally reflectingsurface and engaging the whole beam. The composite beam is a centralflat beam from the flashing source and a beam separated into two lateralbeams from the constant source, fused accurately in the slit image bythe objective. A collecting lens is interposed between the reflectingsurface and the slit.

PATENIEHJML 6:911

SHEET 1 [1F 2 sumauFz RSEHZBZ? PATENTEDJUL man OPTIAL APPARATUS FORREGULATING rue COMBINATION AND SEPARATION or REFLECTED LUMINOUS BEAMSThis invention relates to a system and device for combining or dividingtwo optical beams.

The addition of a system of recording (photography, cinematography,etc.) or of retransmission (television) to a system of observation(telescope, filed glasses, microscope, etc.) or

so-called reflex viewers is generally done by the interposition into thepath of the light rays which traverse the principal system, of a movablereflecting element or fixed semireflecting element, inclined so as tocause either the deflection of the beam, or its division in order toform a second beam of light rays similar to the first, but spaciallydisplaced.

A similar system is used in reverse manner also to produce, whererequired, and in particular in the case of microphotography, thecombination of a permanent illuminating means used during observationand during focusing and of a special illuminating means for therecording of the image (flashbulb in particular).

The movable reflector system has obviously the drawback of being complexand cause a flickering of the observed image.

The fixed semireflector system has obviously the drawback of a loss oflight which, for certain applications, is unacceptable. In fact, thisloss of light acting as a filter does not dispense with the need to stopdown or narrow the recording light beam to obtain a sufficient depth offield, while the eye of the observer obtains this depth byaccommodation. The solution which consists of sacrificing theobservation for the benefit of the recording by adopting a coefiicientof reflection different by 50 percent is not acceptable either incertain cases where it renders precise focusing impossible.

It is an object of the present invention to obviate the aforesaiddrawbacks.

According to the invention there is provided a method for thecombination or division of two optical beams intended, one for thepermanent illumination of an image for the observation of this image andthe other for the instantaneous illumination of this image for itseither photographic or cinematographic recording.

This method consists of arranging at the point of convergence or ofseparation of two optical beams a reflecting element of which thesurface is a regular portion of the nonreflected section of the beam,this element being inclined so as to deflect the reflected beam into theaxis of the nonreflected beam, at the point of combination of the twobeams, and to deflect the reflected beam into a different direction fromthat of the nonreflected ray, at the point of separation of the beams,this reflecting element thus ensuring the stopping down or narrowing ofthe reflected beam which is, on that account, intended for theinstantaneous lighting or for the recording of the image, while theother beam is intended for the permanent illumination or for theobservation of this image.

According to another aspect of this invention a device for the operationof thismethod is constituted by an optical element comprising a totallyreflecting surface which occupies geometrically only a part of the crosssection of the total emergent of incident beam.

In one simple embodiment of the invention, this device is constituted bya rectangular prism on the inside of which is inserted an inclinedreflecting surface.

Advantageously, especially in the case where this process is applied toa photographic ocular biomicroscope with slit lamp, the device used forthe combination of the optical beams comprises a reflecting surface ofrectangular profile of very small width and that used for the separationof optical beams comprises a reflecting surface of elliptic profile.

Advantageously, the slit lamp comprises a collecting lens interposedbetween the inclined reflecting surface and the slit,

in such manner that this latter is situated at least approximately atthe site of the collecting lens.

In order that the invention may be more fully understood, an embodimentof a device incorporating a system according to the invention isdescribed below, purely by way of an illustrative but nonlimitingexample, with reference to the accom panying drawing, in which:

FIG. I is a side view in axial section of an ocular biomicroscope, witha slit lamp, and equipped with an embodiment of a device employingsystems according to the invention;

FIG. 2 is a view along the arrow A of FIG. 1 of the device according tothe invention, used for the separation of the optical beams in themicroscope;

FIG. 3 is a view along the arrow B of FIG. 11 of the device according tothe invention, used for the combination of the optical beams, in theslit lamp; and

FIG. 4 is a diagrammatic perspective view illustrating the operatingprinciple of the ocular biomicroscope with the slit lamp of FIG. 1.

Referring first to FIG. 4, as in all biomicroscopes, the slit lampprojects into the examined eye 1 a flat light beam 2 emerging from aslit 3 which determines in the optical media of the eye an opticalsection which is examined with the aid of the microscope. The latterpossesses a photographic device.

The flat light beam 2 emerging from the slit 3 is focused in the opticalmedia of the eye by the objective 4 which forms the image 5 of the slit3. As is seen, in FIG. 4, the optical section observed is in reality thevolume of the optical media bounded by light rays which join the edgesof the image of slit 5 at the edges of the free opening of the objective4. But the sharpness of this optical section is inversely proportionalto its thickness. In the immediate neighborhood of the image 5 of theslit, this thickness can be:easily controlled by acting on theadjustable width of the slit 3. It is not the same either when spacedmore in front or behind the slit image 5, since then the light beamtakes a form of which the cross section tends to approximate to that ofthe objective 4. To limit this drawback, the slit lamp is provided witha rectangular diaphragm 6 the slit of which is longitudinally parallelto the slit 3, so that the light beam preserves a rectangular crosssection. Nonetheless, it remains necessary to accept a compromisebetween the reduction of lighting and the gain in depth of fieldresulting from the interposition of the diaphragm 6.

However, it may be noted that observation is less demanding in depth offield than photography, by reason of the possibility of exploring thevarious portions of the eye with a distinct section of limited extend,while photography necessitates representation in a single image ofsatisfactory distinctness an optical section extending for exampleacross the whole crystalline lens of the eye.

For flash photography, the invention supplies a solution to the problemof the combination of light beams emerging from one part of thepermanent luminous source of observation 8 and on the other hand, of theflashing light 7, by effecting in the resulting common beam, at each ofthese beams a shape and a position corresponding to the requirements oftheir own use.

As regards the microscope, the invention supplies also the solution ofthe same problem. The microscope is focused in principle, on a welldetermined plane, buy by reason of its accommodation of the limit ofseparating power and of visual accuity, there is in reality in theobject space a volume of a certain depth which is sharply seen by theeye of the observer, If it is desired that the recorded image restore atleast the quality of the observed image, it is necessary to be sure thatthe depth of filed of the beam directed towards the receiver is greaterthan that of the beam directed towards the observer.

There also, the invention ensures the separation of the two beams in amanner which corresponds perfectly to the requirements of their own use.

In the apparatus shown, the invention is realized in the followingmanner:

The slit lamp comprises:

A. a permanent light source b which, through the condenser 9, the mirrorlit), the parallel faced prism ill, a second mirror 12 and a collectorl3 illuminates the slit 3 from which the objective 4 forms the sharpimage 5 in the examining eye. The diaphrgm 6 gives the beam projectedinto the eye a rectangular section.

B. a flashbulb 7 of which the luminous flux projected through thecondenser 14 is reflected on an inclined surface 15, contained in theprism ill to follow then the same path as the emergent beam from thepermanent source 8. According to the invention, the reflecting surface15 only obturates a central portion of the cross section of thepermanent lighting beam. For this application, the subdivision is donein the form of 3 parallel bands, that is to say a central band is forthe flashlamp framed by two side bands 16a and lltib for focusing.

Moreover, the slit 3 is placed substantially at the focal point of thecollector 13 so that the light rays which can pass through the slit 3when it is adjusted to be very narrow through the prism 11 parallel to amedian plane passing through the optical axis and through the slit, thisarrangement having the effect of producing a flat light beam ofrectangular section from a reflecting surface 15 with parallel edges,without the inclination of the said reflecting surface 115 introducing adistortion of the section of the said beam.

Additionally, the prism 11 can occupy two other positions. The prism 1 1is slidably supported for bringing into the beam: either a half-silveredzone 17, for photographs other than in optical section, or forobservations with light reduced by 50 percent, or the zone 18 completelytransparent for observations with full illumination, withoutphotography, or for cinema by boosting the intensity of the permanentsource 8.

The microscope comprises: Behind an optical protecting glass 19, arevolving turret with two paris of objectives 20, a pair of systems ofprisms 21 an eyepieces 22 constituting a conventional stereo-microscope.Behind the objectives of the left half-microscope is interposed theparallel-faced prism 23 enclosing the reflecting surface 24 whichaccording to the invention directs beam 29 through the lens 25 on to thereceiver 26, which beam 29 is the central portion of the beam directedat surface 24, while the peripheral portion continues to be directedtowards the eye of the observer. in this application, the subdivision iseffected concentrically with the optical axis, the beam 29 beingdirected towards the receiver 26 having a solid round section, of smalldiameter and the beam surrounding the beam directed at surface 24 beingdirected towards the observer of annular section.

There again, to effect pure observations without recording, with fullillumination, the reflecting surface 24 must by shifted by making theprism 23 slide so that the light beam passes directly through the freeportion 28 to go entirely towards the left eye of the observer.

The right semimicroscope comprises a fixed plate with compensatingparallel faces, of the same thickness as the prism 23.

it will be understood that various changes and modifications may be madein the embodiments described without departing from the essentialconcept of the invention as defined in scope by the appended claims.

I claim:

1. An optical system for observation and photography, said systemcomprising: a permanent illumination source for providing a prolongedoptical beam; a flashing illumination source for providing aninstantaneous optical beam; first means for directing said instantaneousoptical beam at said prolonged optical beam to intersect and combinetherewith; second means for directing the combined prolonged andinstantaneous optical beams in a prescribed common path; said firstmeans including two spaced at least partially transparent elements, anda reflecting element interposed therebetween, said reflecting elementbeing adapted for reflecting said instantaneous optical beam in aprescribed direction and for dividing said prolonged optical beam intotwo spaced prolonged beams passing one through one of each of saidtransparent elements in said prescribed direction, to them combine withsaid reflected instantaneous optical beam, said reflected instantaneousoptical beam thereby constituting the central portion of the combinedbeam; and third means in said prescribed path for receiving the combinedbeam; said third means including an inner reflecting portion, and anouter portion being at least partially transparent, said inner portionbeing adapted for separating and reflecting said central portion fromthe combined beam to provide instantaneous illumination for photography,and said outer portion being adapted for transmitting the prolongedillumination of the remaining portion of the combined beam to anobserver.

2. A system as claimed in claim 1, wherein said reflecting element ofsaid first means includes a surface which is inclined relative to thepath of optical reflection of the instantaneous beam reflected thereby.

3. A system as claimed in claim 1, wherein said inner reflecting portionof said third means includes a surface which is inclined relative to thepath of optical reflection of the instantaneous beam reflected thereby.

4. A system as claimed in claim 2, wherein said surface of saidreflecting element of said first means is rectangular having a length,and a width being substantially smaller than said length.

5. A system as claimed in claim 3, wherein said surface of said innerreflecting portion of said third means is elliptical.

6. A system as claimed in claim 1, wherein said first means and saidthird means each include a respective prism of rectangular cross sectioninternally of each of which is supported said reflecting element andsaid inner reflecting portion respectively.

7. A system as claimed in claim 1, wherein each said prism is slidablysupported for removing the reflective surfaces of said first and thirdmeans from the path of the beams, and each said prism includes apartially transparent surface movable into the path of the beams toreplace the reflecting surfaces of said first and third means.

8. A system as claimed in claim 4, wherein each of said partiallytransparent elements of said first means are rectangular and areoperatively associated with the rectangular reflecting elementinterposed therebetween for combining said instantaneous and prolongedbeams into a combined rectangular beam.

9. A system as claimed in claim 8, wherein said second means includesfocusing means for accurately fusing said central portion of thecombined beam with the outer portions thereof into a combined narrowrectangular beam.

10. A system as claimed in claim 9, wherein said second means includes aslit adjusting means spaced opposite said focusing means at the focalpoint thereof for adjusting the width of said combined narrowrectangular beam passing therethrough.

1. An optical system for observation and photography, said systemcomprising: a permanent illumination source for providing a prolongedoptical beam; a flashing illumination source for providing aninstantaneous optical beam; first means for directing said instantaneousoptical beam at said prolonged optical beam to intersect and combinetherewith; second means for directing the combined prolonged andinstantaneous optical beams in a prescribed common path; said firstmeans including two spaced at least partially transparent elements, anda reflecting element interposed therebetween, said reflecting elementbeing adapted for reflecting said instantaneous optical beam in aprescribed direction and for dividing said prolonged optical beam intotwo spaced prolonged beams passing one through one of each of saidtransparent elements in said prescribed direction, to them combine withsaid reflected instantaneous optical beam, said reflected instantaneousoptical beam thereby constituting the central portion of the combinedbeam; and third means in said prescribed path for receiving the combinedbeam; said third means including an inner reflecting portion, and anouter portion being at least partially transparent, said inner portionbeing adapted for separating and reflecting said central portion fromthe combined beam to provide instantaneous illumination for photography,and said outer portion being adapted for transmitting the prolongedillumination of the remaining portion of the combined beam to anobserver.
 2. A system as claimed in claim 1, wherein said reflectingelement of said first means includes a surface which is inclinedrelative to the path of optical reflection of the instantaneous beamreflected thereby.
 3. A system as claimed in claim 1, wherein said innerreflecting portion of said third means includes a surface which isinclined relative to the path of optical reflection of the instantaneousbeam reflected thereby.
 4. A system as claimed in claim 2, wherein saidsurface of said reflecting element of said first means is rectangularhaving a length, and a width being substantially smaller than saidlength.
 5. A system as claimed in claim 3, wherein said surface of saidinner reflecting portion of said third means is elliptical.
 6. A systemas claimed in claim 1, wherein said first means and said third meanseach include a respective prism of rectangular cross section internallyof each of which is supported said reflecting element and said innerreflecting portion respectively.
 7. A system as claimed in claim 1,wherein each said prism is slidably supported for removing thereflective surfaces of said first and third means from the path of thebeams, and each said prism includes a partially transparent surfacemovable into the path of the beams to replace the reflecting surfaces ofsaid first and third means.
 8. A system as claimed in claim 4, whereineach of sAid partially transparent elements of said first means arerectangular and are operatively associated with the rectangularreflecting element interposed therebetween for combining saidinstantaneous and prolonged beams into a combined rectangular beam.
 9. Asystem as claimed in claim 8, wherein said second means includesfocusing means for accurately fusing said central portion of thecombined beam with the outer portions thereof into a combined narrowrectangular beam.
 10. A system as claimed in claim 9, wherein saidsecond means includes a slit adjusting means spaced opposite saidfocusing means at the focal point thereof for adjusting the width ofsaid combined narrow rectangular beam passing therethrough.